Penicillins Derived from Penicillium Fungi Were the First Available $\beta$ -Lactam Antibiotics, Which Inhibit the Biosynthesis of the Peptidoglycan Layer

Multiple Choice

Penicillins derived from Penicillium fungi were the first available $\beta$ -lactam antibiotics, which inhibit the biosynthesis of the peptidoglycan layer of bacterial cell walls. Which detail of the structure of penicillin is the "lactam-unit"?

A) I
B) II
C) III
D) IV